n = 26 x 25 x 10 x 9 x 8=468000.
i.e. there are twenty-six choices for the first letter, but only twenty-five choices for the second letter which must be different from the first letter. Similarly, choices for the digits are 10, 9 and 8 since the digits must be distinct.

23:

Suppose a licence plate contains two letters followed by three digits with the first digit not zero. How many different licence plates can be pinted?